Well I thought I'd revisit this old thread! My original post said I knew I would have a 16v or a 500E, though I don't know how I would pay for it. A few months later I won a car which I sold. I sat on the money for a while but eventually 18 months ago bought a 2.5-16.
I think I made the right choice for me. It's great fun but sensible enough to use everyday (though the drivetrain can be jerky). It's reasonably cheap to run - certainly compared to a 500E - and still feels quite special. It's not massively fast, at least not in a straight line, but its handling once you get used to it means you can keep up with much faster stuff. It is brilliant fun to drive, yet rides beautifully.
There are no excuses to make for it, except perhaps the relative lack of torque, and even in standard form on track it doesn't feel heavy and is well balanced. It's also very forgiving so inspires confidence.
As a bonus the 2.3-16 and 2.5-16 seem to be gaining popularity in the UK. It attracts a surprising amount of attention of the right sort. And I like to think I regularly take by surprise those who have no clue what it is
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I haven't driven a 500E yet but really hope to one day. I've driven the W140 S500 and was disappointed. It didn't feel as fast as I was expecting and needed 'winding up' (higher revs) to feel like it had 5.0 litres. It was only a brief drive though so I probably was expecting a bit much in the 15 minutes I had.
Likewise the R129 SL500 was similarly disappointing. It was quicker but again didn't thrill anything like I expected. But again more time with it would probably help. I wonder therefore if the 500E can thrill or if I'm just more into lighter cars.